Monday, January 14, 2008

how to pour soda on ice

Have you ever noticed that you can pour soda directly into a cup of ice at most restaurants, but when you try it at home, your cup fizzes out the wazoo and all your carbonation is gone, like so many childhood daydreams dashed by the cruel, merciless fist of fate?

As a dedicated soda fan, this problem used to present no small helping of consternation at mealtime. Alas, by experimentation and some web browsing, I found that one small factor makes all the difference -- the surface quality of the ice itself. If you simply make sure your ice is wet (no, ice is not always wet) then you will have copious carbonation upon pouring. Check out the video for some (informal) experimental evidence.

The inquisitive reader may inquire at this point: (a) how does that explain the way restaurant pouring works? and (b) why does this work at all?

(a) I believe many restaurants store ice not in a freezer, but rather in a bucket or other receptacle from which it may be easily dispensed. By allowing the ice to start thawing, the surface begins to melt, so that the ice is covered by a thin layer of water (i.e. it's wet).

(b) Rob Landolfi describes the action of the surface of the ice as a collecting point for carbon dioxide molecules. CO2 is non-polar, as opposed to H2O, so that when a bubble of the gas starts to form within the liquid, it leads to a cascading effect (more CO2 is likely to run into a large gas bubble) which results in a larger bubble that rises to the surface and escapes. In the absence of a rough surface to catch a few CO2 molecules, they are more likely to never hit each other, and the bubbles are less likely to form.

Notice in the experiment that many factors remain the same -- the temperature of the soda, the number of ice cubes, the surface area of the ice and the glass -- even the temperature of the ice itself remains very similar. This should debunk some other possible hypotheses about how ice removes carbonation.